Significant development has been made in printing technology since its origin as one of the Four Great Inventions in ancient China.
The present printing process generally includes the following steps: 1. substrate transport and printing preparation for single-color or multi-color printing process; 2. first color (or background color) printing: transfer the printing ink of a first printing station to the substrate by printing plate (or screen); 3. drying by forced or natural evaporation to remove water and organic solvents from the printing ink by heating, ventilation and so on; 4. second color printing: transferring the printing ink in a second printing station to the suitable positions of the substrate by printing plate (or printing screen) followed by drying; 5. performing other printing processes.
With regard to the current printing technology, poor surface flatness of substrates (e.g., paper, fabrics, nonwoven paper and plastic thin film) would directly influence the printing quality. As for substrates with rough surface, such as kraft paper, fabrics and nonwoven paper, the surface is generally not in complete contact with the printing plate, resulting undesirable consequences such as discontinuous and white leak after printing, significantly affecting printing precision and hindering further progress.
Generally, the problems mentioned above are solved by improving papermaking process to increase paper flatness. However, such measures increase manufacturing cost, yet not completely resolving the problems of printing quality.
The printing of nonwoven fabric material, a high-end product in architectural decoration industry, also encounter the same problems because such materials have irregular surface with fiber structure designed to catch people's eyes as elegant works of art. And yet it is exactly the surface irregularity that results in poor contact between the concave portion on the surface and the printing roller during substrate inking and therefore causes small breaks or large areas of white points in the printed portion, especially for patterns with dark background, greatly deteriorating the printing effect as a whole.